The general consensus I've seen here on HN is that Boeing should have done a clean sheet design rather than trying to shoehorn increasingly ill-fitting features into a decades-old design. You're not accurately representing that view.
"American also intends to order 100 of Boeing's expected new evolution of the 737NG, with a new engine that would offer even more significant fuel-efficiency gains over today's models. American is pleased to be the first airline to commit to Boeing's new 737 family offering, which is expected to provide a new level of economic efficiency and operational performance, pending final confirmation of the program by Boeing. This airplane would be powered by CFM International's LEAP-X engine."
Then taking umbrage here that they were too conservative and possibly froze the hardware spec.